Abstract
MAX2 (MORE AXILLARY GROWTH2) is involved in diverse physiological processes, including photomorphogenesis, the abiotic stress response, as well as karrikin and strigolactone signaling-mediated shoot branching. In this study, MdMAX2, an F-box protein that is a homolog of Arabidopsis MAX2, was identified and characterized. Overexpression of MdMAX2 in apple calli enhanced the accumulation of anthocyanin. Ectopic expression of MdMAX2 in Arabidopsis exhibited photomorphogenesis phenotypes, including increased anthocyanin content and decreased hypocotyl length. Further study indicated that MdMAX2 might promote plant photomorphogenesis by affecting the auxin signaling as well as other plant hormones. Transcripts of MdMAX2 were noticeably up-regulated in response to NaCl and Mannitol treatments. Moreover, compared with the wild-type, the MdMAX2-overexpressing apple calli and Arabidopsis exhibited increased tolerance to salt and drought stresses. Taken together, these results suggest that MdMAX2 plays a positive regulatory role in plant photomorphogenesis and stress response.
Highlights
Apple tree (Malus × domestica) is one of the most important economic crops in the world and is used to provide both fruit and woods (Wang et al, 2015)
Amino acid sequence analysis showed that MdMAX2 contained an F-box motif in its N-terminus and two leucine-rich repeat (LRR) repeat motifs in its C-terminus that were highly conserved in a variety of plant species (Figure 1A; Supplementary Figure S1)
The results suggested that MdMAX2 was most closely related to the Pyrus bretschneideri PbMAX2 protein
Summary
Apple tree (Malus × domestica) is one of the most important economic crops in the world and is used to provide both fruit and woods (Wang et al, 2015). The cultivation and yield of apple is frequently limited by various external environmental factors, such as light, temperature, and nutrients. Numerous genes are induced by external environmental factors to regulate plant growth and development (Xiong et al, 2002; Todaka et al, 2015). It is necessary to study the functions of genes that are regulated by external environmental factors to improve crops’ adaptation to the variable environment. Depending on the different light conditions, plants exhibit two contrasting growth statuses: skotomorphogenesis in the dark and photomorphogenesis in the light. Skotomorphogenesis is characterized by elongated hypocotyls and closed cotyledons. Photomorphogenesis is characterized by shortened hypocotyls and open cotyledons
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